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2 days ago · For example, certain evolutionary pathways may not be possible due to the organism’s existing genetic or developmental framework. These constraints shape how evolution can unfold in different lineages. Evolution Examples. Evolution is seen in many species across different environments.
- Overview
- The evidence for evolution
evolution, theory in biology postulating that the various types of plants, animals, and other living things on Earth have their origin in other preexisting types and that the distinguishable differences are due to modifications in successive generations. The theory of evolution is one of the fundamental keystones of modern biological theory.
The diversity of the living world is staggering. More than 2 million existing species of organisms have been named and described; many more remain to be discovered—from 10 million to 30 million, according to some estimates. What is impressive is not just the numbers but also the incredible heterogeneity in size, shape, and way of life—from lowly bacteria, measuring less than a thousandth of a millimetre in diameter, to stately sequoias, rising 100 metres (300 feet) above the ground and weighing several thousand tons; from bacteria living in hot springs at temperatures near the boiling point of water to fungi and algae thriving on the ice masses of Antarctica and in saline pools at −23 °C (−9 °F); and from giant tube worms discovered living near hydrothermal vents on the dark ocean floor to spiders and larkspur plants existing on the slopes of Mount Everest more than 6,000 metres (19,700 feet) above sea level.
The virtually infinite variations on life are the fruit of the evolutionary process. All living creatures are related by descent from common ancestors. Humans and other mammals descend from shrewlike creatures that lived more than 150 million years ago; mammals, birds, reptiles, amphibians, and fishes share as ancestors aquatic worms that lived 600 million years ago; and all plants and animals derive from bacteria-like microorganisms that originated more than 3 billion years ago. Biological evolution is a process of descent with modification. Lineages of organisms change through generations; diversity arises because the lineages that descend from common ancestors diverge through time.
The 19th-century English naturalist Charles Darwin argued that organisms come about by evolution, and he provided a scientific explanation, essentially correct but incomplete, of how evolution occurs and why it is that organisms have features—such as wings, eyes, and kidneys—clearly structured to serve specific functions. Natural selection was the fundamental concept in his explanation. Natural selection occurs because individuals having more-useful traits, such as more-acute vision or swifter legs, survive better and produce more progeny than individuals with less-favourable traits. Genetics, a science born in the 20th century, reveals in detail how natural selection works and led to the development of the modern theory of evolution. Beginning in the 1960s, a related scientific discipline, molecular biology, enormously advanced knowledge of biological evolution and made it possible to investigate detailed problems that had seemed completely out of reach only a short time previously—for example, how similar the genes of humans and chimpanzees might be (they differ in about 1–2 percent of the units that make up the genes).
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Darwin and other 19th-century biologists found compelling evidence for biological evolution in the comparative study of living organisms, in their geographic distribution, and in the fossil remains of extinct organisms. Since Darwin’s time, the evidence from these sources has become considerably stronger and more comprehensive, while biological disciplines that emerged more recently—genetics, biochemistry, physiology, ecology, animal behaviour (ethology), and especially molecular biology—have supplied powerful additional evidence and detailed confirmation. The amount of information about evolutionary history stored in the DNA and proteins of living things is virtually unlimited; scientists can reconstruct any detail of the evolutionary history of life by investing sufficient time and laboratory resources.
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Evolutionists no longer are concerned with obtaining evidence to support the fact of evolution but rather are concerned with what sorts of knowledge can be obtained from different sources of evidence. The following sections identify the most productive of these sources and illustrate the types of information they have provided.
- Francisco Jose Ayala
Dec 18, 2021 · Ultimately, natural selection leads to greater adaptation of the population to its local environment; it is the only mechanism known for adaptive evolution. Papers by Darwin and Wallace (Figure 17.2.2 17.2. 2) presenting the idea of natural selection were read together in 1858 before the Linnean Society in London.
- Fossils. The discovery of the first fossil firmed the concept of evolution, baffling everybody. Since then, many remarkable discoveries have been made with fossils that turned out to be the preserved remains of the distant ancestors of present-day organisms.
- Homologous Structures. A bird’s wing, a dolphin’s flipper, and a human arm have similar basic bone structures but serve different functions. Such structures are called homologous structures and support the theory of common ancestry between the two species.
- Vestigial structures. Vestigial structures are the remnants of their ancestral structures that are no longer functional. However, they explain the adaptation in the lineage and hence validate evolution.
- Analogous Structures. As opposed to homologous structures, analogous structures have similar functions but different structures. Their analogy or homoplasty occurs due to environmental limitations rather than a close evolutionary relationship.
Oct 31, 2023 · The theory of evolution is the unifying theory of biology, meaning it is the framework within which biologists ask questions about the living world. The Ukrainian-born American geneticist Theodosius Dobzhansky famously wrote that “nothing makes sense in biology except in the light of evolution.”. The tenet that all species have evolved and ...
Aug 24, 2022 · Figure 3.1.1 3.1. 1: All organisms are products of evolution via adaptations to their environment. (a) Saguaro (Carnegiea gigantea) can soak up 750 liters of water in a single rain storm, enabling these cacti to survive the dry conditions of the Sonoran desert in Mexico and the Southwestern United States.
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Mar 17, 2024 · Evolution is the process of change in living organisms over generations. It is driven by natural selection. Evolution remains one of the most significant concepts in biology, explaining the diversity of life on Earth. The theory of evolution, proposed by Charles Darwin, suggests that all species have descended from a common ancestor through a ...
